Persistent Luminescence Induced by Upconversion: An Alternative Approach for Rechargeable Bio‐Emitters

The charging of persistent luminescence using an infrared laser as a power source and an upconversion process is a recently proposed trend in the field of persistent luminescence that allows expansion of the potential applications for these materials. In bioimaging at nanoscale, it allows for increased rechargeability capacity, as the excitation wavelength is fully inside the biological window. In this work, a novel approach is proposed to this phenomenon using energy transfer on associated materials. For this purpose, β‐NaGd0.8Yb0.17Er0.03F4 nanoparticles, known for their efficient upconversion, and Zn1.33Ga1.335Sn0.33Cr0.005O4 nanoparticles, known for their persistent luminescence properties, have been synthesized and associated through a dry impregnation method. The obtained hybrid material is found to present persistent luminescence at 700 nm after charging with a 980 nm laser. A mechanism is proposed to explain this energy transfer process and the capabilities of the hybrid material as rechargeable persistent nanoprobe for in vivo applications are shown. A composite made of a persistent luminescent material and an upconverting material is analyzed. With near infrared excitation source, it is found to be possible to charge the deep‐red persistent luminescent material via energy transfer from the Yb3+/Er3+ upconversion system, toward Cr3+. The potential of such a phenomenon for in vivo optical imaging is demonstrated.